1. Field of Invention
The invention relates to a color chamber doctor blade.
2. Description of the Prior Art
Color chamber doctor blades have been known for a long time. The color chamber doctor blades are subject to continuous wear and therefore must be replaced regularly. As a rule, to fix them, the doctor blade knives are pressed against the doctor blade chamber body with the help of a clamping plate. For that purpose, in the past, the clamping plates were fixed with screws on the doctor blade chamber body, as shown in DE 42 41 792 A1. The clamping plate, in its turn, presses the doctor blade knife against the doctor blade chamber body and thus fixes it. However, because of the length of the doctor blade in the radial direction of the roller, which is impinged with color from the doctor blade chamber, a large number of screws must be changed when changing the doctor blades. Since all kinds of set-up times lead to machine still stand and, as a result, are expensive, various suggestions for devices have been made in the literature that permit faster exchange of the doctor blade knives. Thus, in DE 43 20 833 C1S use of rapid-action locking devices is suggested. In recent times, one finds that the aforementioned types of fixing the clamping plates of the doctor blade knives on the doctor blade chamber body are being replaced, such that                the clamping plate is in active connection with long-stretch fasteners in the axial direction (z) of the roller,        which are mounted essentially parallel to the clamping plate        and by which the force necessary for fixing at least one of the doctor blade knives is exercised,        
Clamping plates are flexible sheet metal plates that are held by means of screws or similar means of fastening on the doctor blade chamber body, however, they are not permanently fixed. Clamping is done on the side of the screws facing the roller, whereby the long-stretch fasteners in the axial direction (z) of the roller exert force on the clamping plate, which points away from the doctor blade chamber body. The clamping plate is, however, fixed on the doctor blade chamber body by the screws, so that the clamping plate buckles and exerts force on the doctor blade knife, on the side of the screws facing the roller, which is mounted on the doctor blade chamber body and thus fixes the doctor blade knife on the doctor blade chamber body. If the force exerted by the long-stretch fasteners is inhibited, force is also neither exerted on the doctor blade knife and, if applicable, on the clamping plate.
In general, the long-stretch fasteners in the axial direction (z) of the roller are rods, with a partially round cross section, which are supported rotatably in the doctor blade chamber body. Such rods are then provided with a recess or a projection, which leads to it that, on rotation of the rod, a force is exerted, whose resultant points away from the doctor blade chamber. However, it is also possible to place an inflatable hose or an another body at that point, which can increase its volume, and in that way, exert a force on the clamping plate, whose resultant points away from the doctor blade chamber body.
Finally it should be emphasized again that the major advantage of this type of fastening is that, compared to the fixing of the doctor blade knife by loosening screws, significantly lesser number of objects of fastening—such as the rod for instance—need to be handled, so that it leads to significant saving of time in the changeover of the knives.
However, the described fastening systems also have their disadvantages.
As it is apparent from the above explanation and the following description of the situation, a large number of screws or similar fasteners must be pushed at least through the clamping plate for the above mentioned prefixing of the clamping plates. Therefore, the described doctor blade chambers have a number of holes and juts (screws) in the area of the clamping plates. Naturally, due to the unavoidable mass of the residues of the color exiting from the color deck, color deposits precipitate precisely on the holes and the juts (screws), which make it difficult to cleanse the machine and, to some extent, also to change the knives.
Consequently, the task of the present invention is to devise a doctor blade chamber, which can function with a lesser number of holes and juts (screws) in the area of the clamping plates.